Hydrocarbon compositions



2,934,415 HYDRQCARBON COMPOSITIONS PauLC-Wilhelmsen, Pleasant Hill, Califi, assignor to Shell Oil Company, a corporation of Delaware No Drawing. Application September 17, 1956 a Serial No. 610,404

7 Claims. (Cl. 44- l) during blending operationspstorage, and transportation.

'to the'consum'er. Also, even if the greatest precautions ii'to preventany such contact were taken, water would still be absorbed from the atmosphere. .The presence of a small amount of water as such is not normally deleterious;

,. v I however, when the product is cooled, ice particles often" 1 are formed.

The formation of ice in such hydrocarbon productsis iusually at least. troublesome and "often is extremely I" dangerous. For example, all vehicles powered by gasoline," kerosene, jet fuel or diesel fuel are normally prowided'with'filters, such as filter screens and micronic i. filters, in the fuel system, so as to prevent the passage of solid'contaminants, for example, small particles of rust, aillfO the engine. At low temperatures, ice will often :5plu'g thesefilters, thus stopping the flow of fuel to the engine. i In the case of vehicles operating on the ground lorwater surface, this is at leastinconvenient; butin air- ".craft'such stoppage, of course, involves av grave risk to J; human lifeJBecause of this danger, most aircraft are provided withan automatic by-pass around the fuel sysatern, filters. However, on the opening of the by-pass, athe. ice m'ayfoulthe injector mechanisms and the like whichco'ntain close and critical tolerances.

Another fuel system mechanism which is particularly .prone' to malfunctioning due to plugging with ice is the Ccarburetor. At this point ;in the'fuel system, additional moi sture;i s introducedin the combustion air. Even though both liquid fueland air temperatures are above 32 F.,, the evaporation ofthe fuel in the carburetor will oftencool the system to 32 F. or below, especially at a -=time soon after starting the engine, whereupon ice will g form and will frequently cause the engine to stall because ofthe blocking of fuel and air passages by the ice.

Heretoforethese difiiculties have sometimes been alleviated ;by incorporating into the liquid hydrocarbon distillate certain water-soluble freezing point depressants,-

t such as low molecular weight alcohols, including glycols, -or the likep However, this requires relatively large conftzentrationsof the freezing point depressant, for example, from about 0.l% to as hight as 2 or 3% by volume. Theseflargeconcentrations are not only uneconomical llbutalso often adversely. elfect the chemical and physical 1 propertiesof the distillate. Additionally, the high af- Tfinityof these compounds forwater makes them susceptg'frernov'al' from the distillate by the leaching ac- R 2,934,415 .P t t Ap 6.,

' tion of the free water with which distillates usually come in contact during storage. Furthermore, such compounds when incorporated into the hydrocarbon distillate act as solubilizers for water, thus actually increasing 5 the amount of w ter which the distillate will absorb during commercial handling. Although this is by no means desirable, addition of some of the alcohols, for example, isopropyl alcr ml, to fuels, is nevertheless somewhat effective in decreasing the incidence of stalling of automobiles due to carburetor icing. But in the case of aircraft applications, wherein filter clogging is particularly critical 1 and temperatures are unusually low, the increased concentration of water in the fuel overbalancesthe benefit of the freezing point depressant, so the addition of the latter often aggravates rather than alleviates the problem.

It is accordingly a principal object of this invention to I provide an improved liquid hydrocarbon distillatez'comp'osition; A more particular object is to.provid'e.s'uch a composition. which has improved. characteristics. with ..respect to ice formation therein. Another objectloflhe invention is to provide a hydrocarbon composition with improved characteristics with respect to ice formation therein and which does not require a high concentration of an anti-icing additive. Still another object is to provide an improved hydrocarbon distillate fuel composition suitable for use in internal combustion engines. Other objects will be apparent from the description of the invention.

It has now been discovered that these and other objects are attained by the addition to liquid hydrocarbon distillates of an extremely small concentration,i'.e.,-'less I than 10 parts vper million by weight, of a certain class of inorganic crystalline materials to be described with particularity hereinafter.

The mechanism by which the additives of the invention are effective is not known with certainty. It appears likely that their presence does not actually prevent the formation of ice; in fact, it is likely that they accelerate ice formation. Nevertheless, the presence of these addi- 40 tives prevents, or at least reduces, difliculties experienced in the use of hydrocarbon distillates such as plugging of fuel filter screens and interference with the operationof pumps, injector mechanisms, carburetors and the like.

A probable mechanism is the nucleation of .small droplets of supercooled water suspended in the liquid distillate, or in the case of carbureter icing in the air-fuelmixture, whereby the ice particles which do form are.,so small that they pass through the system in whichthe distillate is used without causing difficulties.

50, The liquid hydrocarbon base material which is the major component of the composition of the invention can be any hydrocarbon or mixture of hydrocarbons boiling below the lubricating oil boiling range, i.e.,'those boiling substantially within the liquefied petroleum gas, gasoline, kerosene, aviation turbine fuel (jet fuel) and diesel fuel boiling range, that is, those with normal boiling points within the range of from about F. to about 700 F. The invention is particularly directed to mixtures of hydrocarbons boiling within an ASTM boiling range of from about F. to about 600 F.,'such as aviation turbine fuel (jet fuel), gasoline, and especially such as aviation gasoline, which normally has an ASTM boiling range of from about F. to about 350 -F.

More especially, the gasolines in which the additives of 65 the invention are most advantageously incorporated are --the.more volatile gasolines which have 0% distillation a (ASTM v-w r t wash t mar.

asteners especially no gi'eater than 240 F. However, the additives are also suitably and usefully incorporated 'into special boiling point solvents, paint thinners, gas condensate well products, liquefied propane or butane tractor fuels and the like.

The effective additives of the invention are extremely finely divided inorganic crystalline materials which can exist as solids in a liquid hydrocarbon system containing smallfdroplets of dispersed Water, at temperatures encountered in the use of the hydrocarbon product. Thus, they must be soluble to no substantial extent in either liquid hydrocarbon or water, i.e., to a lesser extent than ;1 i-gram, or preferably'less than 0.1 gram, per 100 cc at 32, It should be noted thatgsome materials, while soluble in water or hydrocarbon liquids at normal temperatures, are less so attemperatures at or below the "freezing point pf Water. Such materials, as long as adequate concentrations of the precipitated particles are obtained, are eminently suitable. The additives mustalso be, chemically inert, at ambient temperatures and below, ,to both liquid hydrocarbons and water. f the crystalline materials of the invention, binary compounds, especially inorganic binary salts, are preferred; however, metals, metal alloys and metal oxides also come into consideration.

It-is critical to the invention that the finely *divided "solid additive be-in a crystalline form in the fuel, and 'it must have a space lattice of the hexagonal arrangement.

Additionally, it is necessary that the a parameter of the spacelattice cell be at least 4.00 A. (Angstroms) and no more than 5.00 A. in length. The preferred class of such materials are those in which a is from about 4.380 A. to about 4.650 A., more especially from about 4.470 A. to about 4.560 A. (For the conventional indem'ng of hexagonal crystal dimensions, see Encyclopedia of Chemical Technology, Kirk and Othmer, editors, The Interscience Encyclopedia, Inc, New York, volume 4, page 640, 1949.)

The length of the c parameter of the hexagonal lat 'tice cell is not as important as that of the a parameter, but it is preferably not less than 4 A. or greater than 20 A. Especially effective are crystalline materials in which the c parameter of the cell is from about 6.5 A. to about 7.5 A. in length.

The preferred crystalline materials for the purposes of the invention are lead iodide (Pbi 0 4.53, c=6.93) and silver iodide (AgI, 'a=4.586, c=7;490). Because of its greater chemical stability, lead iodide is especially preferred. However, many other crystalline materials are useful, among which are hexagonal calcium carbonate '(CaCO a=4.983, c=l7.02), rhodium fluoride (RhF 1z4.878, 0:6.809), cadmium sulfide (CdS, a' '=4.l*0, 'c'==6.724), aluminum phosphate (AlPO 11: 1.92, c: 10.91), bismuth (Bi, (1:14.537, 0:11.838), aluminum oxide '(corundum) (A1 0 Zia- 4.75, 0:12.97), and the like.

The'additives of the invention must eeprsem in the term of a large number of'individual particlesper unit volume of the hydrocarbon liquid. While anactual count of particles is impracticable, it is suflicient for the 'purposes of the invent-ion to incorporate into the liquid "hydrocarbon a suificient concentration by weight of particles of a given average particle size to provide a calculated desired particle concentration (i.e., number of particles per unit volume of the liquid hydrocarbon).

'The necessary particle concentration in'the liquid bydrocarbon depends mainly upon the concentration of water present which will separate from'the hydrocarbon during its handling, storage and use. In general, it is desirable to-have present an average of at least'500 particles per cubic centimeter'of liquid hydrocarbon for "each part per million by weight of water Which would separate from the hydrocarbon liquid. This will insure 'thatany'ice'crystalswhich 'are' formed are so small that "thaylwill cause little no difficultydn the handling and use *of the-liquid hydrocarbon. will be-discussed fulfis to aspirate a solution (e.g., in a solvent such as below, the effective particle sizes are so small that it is possible to greatly exceed the particle concentration 'without going beyond very small weight concentrations, and thus it is preferred that the particle concentration is at least 10,000 particles, and especially at least 100,000 particles, per cubic centimeter of hydrocarbon liquid for each part per million by weight of water which might separate.

As already mentioned, the efiective particle size of the crystalline additive is very small. As long as the particles exist in a separate solid crystalline phase the particles can have an average diameter as small as 0.005 micron, although practical considerations in the preparation of the hydrocarbon liquid composition will favor the use of materials with an average particle 'size of 0.05 micron and above, for example, about 0.1'micron to about 0.5 micron. 0n the other hand, it is of course necessary for an effective particleconcentration to remain in suspension during the handling and storage of the hydrocarbon liquid. Thus, it is desirable that at least the above-mentioned particle concentrations have an average particle size no greater than 1 micron and preferably no greater than 0.5 micron, or the additive will tend to settle out, thus lessening the protection against icing difficulties. In order that the additive itself will not interfere with the operation of mechanical units, including filters, in the system, no-more than 10% by weightof the additive particles should have a particle size of-10 microns or more.

It is also desirable for the weight concentration of-the additive to be not greater than about 10 parts per million (10 ppm.) by weight, and preferably not greater than 1 part per million by weight, because higher concentrations of the inorganic material are likely to bring about undesirable side efiects in the use of the hydrocarbon liquid. This is particularly important in the case of fuels 'for internal combustion engines where combustion chamber deposits area problem. Because the particle size of the crystalline additive can be extremely small, the elfective weight concentrations can be much lower than the above preferred maximum. For example, it is necessary to provide only 0.1 part per million by weight of finely divided lead iodide (Pbl specific gravity=6.l6) having an average particle size of 0.5 micron with 60% of the particles having a particle size of 05:01 micron in a '60" AP! gravity gasoline to have an especially eifective composition containing approximately 100,000 individual crystalline particles of lead iodide per cubic centimeter of thegasoline. When the particle size of the lead iodide is-0.l micron, the same small weight concentration provides a particle concentration of about 12,000,000 particles per cubic centimeter, a sufficient particle concentration to prevent or greatly lessen icing difliculties under even the most critical conditions. Practical limitations in particle size generally "require that the weight concentration of the additive be at least0.00l part per million (1 ppm.) by weight, especially at least-0.01pm per-million by weight.

The compositions of the invention-can be' prep'ar'ed in any of the known ways of preparing 'fin'ely divided dispersions'of solids in' liquids. Itis oftenconv'enie'nt first to prepare a concentrate of the'finely dividedcryst'alli'ne material in a liquid hydrocarbon, for'example, taken sene, gas oil, or even alight lubricating oil, using the concentrate to prepare accurate blends of the final distillate composition. -'-For example, a concentrate ofthe crystalline material can be conveniently prepared by "pa'ssing'it with a liquid hydrocarbon through a paint mill or colloi'd mill until the desiredaverage particle sizeis obtained. Another technique which is sometimes 'ii'seacetone-containing NH I as a complexing agent) of the crystalline material into a flame and bubble the smoke through a hydrocarbon liquid while agitating the latter.

Especiallyin' the casecfadditives which"a'r6 biiia'ry 'Aviation Corporation, Part No.-568,509).

salts, it is convenient-to prepare the hydrocarbon distillate composition, or. a concentrate for blending into a of a finely divided crystalline suspension. 2 It is often desirable to add to the concentrate or to .the

final liquid hydrocarbon distillate composition a small amount of a surface active agent which acts as a dispersant for the crystalline material, thus preventing aggregation of the crystalline particles. Synthetic or petroleum sulfonates are especially effective for this purpose. For example, a small amount of lead dinonylnaphthalene sulfonate was used successfully to stabilize asuspension of lead iodide; the resulting suspension was very effective in preventing icing difiiculties. Both nonionic and ionic, i.e., cationic and anionic, surface agents are suitable, and especially those ionic agents wherein one of the ions is the same as one of the ions of the crystalline additive.

Besides the crystalline-material, the hydrocarbon compositions of the invention can, and ordinarily will, contain' other additives, such as the common commercial additives, for example, anti-detonants such as tetraethyl lead, iron carbonyl, dicyclopentadienyliron, xylidene, and N-methyl aniline, lead scavengers such as ethylene dibromide and ethylene dichloride, dyes, spark plug anti-foulants such as tricresyl phosphate, dimethyl xylyl phosphate, and diphenyl cresyl phosphate, combustion modifiers such as alkylboronic acids and lower alkyl phosphates and phosphites, oxidation inhibitors such as N,N'-disecondary-butylphenylenediamine, N n butyl-p-aminophcnol, and 2,6-ditertiarybutyl-4-methylphenol, metal deactivators such as N,N'-disalicylal-1,2-propanediamine, and rust inhibitors such as polymerized linoleic acids and N,C-'disubstituted imidazolines, and the like.

' thereof.

EXAMPLE I In order to investigate the benefits of various additives in decreasing the tendency of liquid hydrocarbon filters to plug with ice, a filter icing test was designed as follows. The apparatus consisted of a constant flow pump which forced the liquid hydrocarbon to be tested through a heat exchanger, where its temperature was reduced to the desired level, usually between about F. and 20 F., and immediately thereafter through a micron paper filter (Bendix Skinner Division, Bendix In this manner air was excluded, thus avoiding any change in water concentration in the liquid hydrocarbon. The flow rate of the liquid hydrocarbon through the filter was held constant in all tests at 38 cc. per minute. The pressure differential across the filter at any time was therefore a measure of the degree to which the filter was plugged with ice.

' The elapsed time before this differential pressure has reached 16 cm. Hg was selected as a measure of the ability of the liquid hydrocarbon composition to avoid plugging of the filter with ice. The higher this figure, of course, the better the composition.

It was found that variations in filter temperature between 0 F. and 20 F. did not have a substantial effect on the elapsed time before filter plugging in this test.

The base liquid hydrocarbon distillate used in this example was an aviation gasoline of specificationMIL- F-5572 (115/145 grade) containing only the specification additives, i.e., tetraethyl lead, ethylene dibromide and 2,6-ditertiarybutyl-4-methylphenol oxidation inhibitor. To this gasoline was added various amounts of a concentrate of lead iodide (hexagonalPbl .prepared by adding 0.25 gram of iodine in 100 .rril. of hexane to 1.ml. of tetraethyl lead in 500 ml. of isooctane. The :average particle size of the crystalline lead iodide formed was about 0.1 micron. The final gasoline blends tested had weight concentrations of lead iodide of 0.04 .p.p.m, 0.1 p.p.m., 0.2 p.p.m., 3.0 ppm. and 5.0.p.p.-m. 'The base gasoline and the blends containing the crystalline lead iodide performed in the filter plugging t'est- .as indicated in Table I.

It will be noted that the higher concentrations, while still greatly beneficial in preventing icing difficulties, were nevertheless somewhat erratic and of lesser effectiveness than would be predicted from the data obtained with the lower concentrations. This is probably because as concentrations are raised the number of particles per unit volume does not increase proportionately due to aggregation of the particles.

EXAMPLE II The above test procedure was followed with various blends of the gasoline and a concentrate of silver iodide prepared by agitation in a Waring Blendor, and also with blends of gasoline and a concentrate prepared by grinding coarse silver iodide with kerosene in an agate mortar. These blends give filter plugging times varying from 1.3 to 1.9 times that of the base gasoline.

EXAMPLE III The above test procedure was followed with a blend of the gasoline and a concentrate of lead iodide prepared from lead iodide which was precipitated from. a solution thereof with sodium iodide in acetone. The filter plugging time obtained with this blend was 3.2 times that obtained with the base gasoline.

I claim as my invention:

l. A liquid hydrocarbon distillate composition consisting essentially of hydrocarbons boiling within the range of from about F. to about 600 F. and con taining a minor amount, at least 0.001 and less-than about 10 parts per million by weight, of a finely divided inorganic crystalline binary salt selected from the group consisting of silver iodide, calcium carbonate and lead iodide and having an average particle size no greater than about 1 micron.

2. Gasoline containing from about 0.001 to about 1 part per million by weight of crystalline lead iodide having an average particle size no greater than about 0.5 micron.

3. Gasoline containing from about 0.001 to about 1 part per million by weight of crystalline silver iodide having an average particle size no greater than about 0.5 micron.

4. Gasoline containing from about 0.001 to about '1 part per million by weight of crystalline hexagonal calciurn carbonate having an average particle size no greater than about 0.5 micron.

5. A liquid hydrocarbon distillate composition in at? itordance with 'cfaim *1, which isr-a'n aviaitib-n turbine fuel.

6. -An aviation turbine fuel containing from about 0.001 to about l par't pe'rrhillibh by weight of crysfalline "lead iodide having anaverageQarticle size no greater than about 0.5 micron "7 A11 hviation t'urbine fuel containing from :about 0.001 to about 1 partperm'illion by weight of crystalline si-lver ibdide having an average particle size 116 gi'eater 'than' 'abon't 0.5 micron.

UNITED STATES PATENTS 

1. A LIQUID HYDROCARBON DISTILLATE COMPOSITION CONSISTING ESSENTIALLY OF HYDROCARBONS BOILING WITHIN THE RANGE OF FROM ABOUT 90*F. TO ABOUT 600*F. AND CONTAINING A MINOR AMOUNT, AT LEAST 0.001 AND LESS THAN ABOUT 10 PARTS PER MILLION BY WEIGHT, OF A FINELY DIVIDED INORGANIC CRYSTALLINE BINARY SALT SELECTED FROM THE GROUP CONSISTING OF SILVER IODINE, CALCIUM CARBONATE AND LEAD IODINE AND HAVING AN AVERAGE PARTICLE SIZE NO GREATER THAN ABOUT 1 MICRO 